This proposal is concerned with identifying the components of the egg that are formed during oogenesis that specify the pattern of cleavage which occurs during the first stages of embryogenesis and which represent the localizations of developmental potential which bias the way in which different regions of the egg will differentiate during embryogenesis. One system that will be investigated is the ctenophore egg. I have worked out a description of how the localizations of developmental potential which specify comb plate cilia cells and photocytes are set up prior to the differential division which restricts these factors to separate blastomere lineages during the first stages of development. This proposal will try to identify the components of the cell where these factors reside before and after they become localized. The other problem that will be studied in this proposal concerns the developmental basis for dextral and sinistral symmetry in gasteropod molluscs. Some investigators feel that symmetry derives from the way in which localizations of developmental potential are set up in the egg during oogenesis. Other investigators believe that it reflects the way in which localizations of developmental potential and inductive relationships are set up as a consequence of cleavage during early development. This proposal will establish which of these viewpoints is most correct.